Method for controlling scale generation amount of metal material in heating furnace, scale generation amount control device, and heating furnace operation method

Abstract

Provided are: a method for controlling a scale generation amount of a metal material to control the scale generation amount to within an appropriate range in a case where a carbon dioxide discharge amount is to be reduced by using hydrogen or ammonia as a fuel gas of a heating furnace for heating the metal material; a scale generation amount control device; and a heating furnace operation method. According to the method for controlling a scale generation amount of a metal material in a heating furnace, the metal material is burner-heated using, as a fuel, a hydrogen-based gas containing in full either one or both of hydrogen and ammonia, the flow rate of the hydrogen-based gas used as the burner heating fuel is set as a heating furnace operating parameter, and the scale generation amount generated on the surface of the metal material is controlled on the basis of the flow rate of the hydrogen-based gas thus set. At least one item selected from a heating time and a heating temperature of the metal material in the heating furnace is also preferably set as a heating furnace operating parameter.

Description

Method for controlling the amount of scale formation on metal materials in a heating furnace, scale formation control device, and method for operating a heating furnace

[0001] The present invention relates to a method for controlling the amount of scale formation on a metallic material in a heating furnace, a scale formation control device, and a method for operating a heating furnace using the scale formation control method.

[0002] In integrated steel works, blast furnace gas discharged from the top of a blast furnace, which reduces iron ore to produce molten iron, as well as by-product gases generated in converters and coke ovens, have been effectively utilized as fuel gases. However, in recent years, with the demand for reduced carbon dioxide emissions, combustion technologies have been required to reduce the amount of by-product gas used. For example, in heating furnaces that heat steel in hot rolling lines of integrated steel works, there is a demand to reduce the amount of by-product gas used and carbon dioxide emissions. In this case, technologies that use hydrogen or ammonia as fuel gas for heating furnaces have attracted attention. In other words, hydrogen and ammonia, which do not contain carbon elements, produce mainly water and nitrogen when burned, and therefore are highly effective in reducing carbon dioxide emissions, and their application to heating furnaces is desirable.

[0003] In a heating furnace, scale (also called oxide scale) forms on the surface of the steel material during the heating process. The scale formed in the heating furnace is also called primary scale, and is removed by a descaling device disposed in a hot rolling line or the like. Therefore, if the thickness of the scale formed in the heating furnace increases, the weight of the steel material to be made into a steel plate product decreases, resulting in a problem of a decrease in product yield.

[0004] On the other hand, impurities generated during casting and foreign matter resulting from mold powder mixed in during casting may be present near the surface of the steel material being charged into the heating furnace. If hot rolling is performed with impurities or foreign matter still present on the surface of the steel material extracted from the heating furnace, these impurities or foreign matter will become caught between the steel material and the rolling rolls, causing defects on the surface of the steel sheet. For this reason, the steel material is scaled in the heating furnace to a certain thickness, and then the surface impurities and foreign matter are removed together with the scale using a descaling device before hot rolling.

[0005] In other words, in steel heating furnaces, it is necessary to control scale generation to an appropriate amount in order to prevent a decrease in product yield by suppressing excessive scale generation, and to suppress the occurrence of surface defects by actively generating a predetermined amount of scale.

[0006] Therefore, in order to solve these problems, techniques for controlling scale formation on the surface of steel materials have been proposed. Patent Document 1 discloses a non-oxidizing heating method for steel materials as a technique for suppressing excessive scale formation, in which high-temperature non-oxidizing gas preheated to a temperature equal to or higher than the temperature of the steel material being heated or substantially equal to the furnace temperature is supplied around the steel material in a heating furnace.

[0007] Patent Document 2 discloses a steel heating furnace that is equipped with a plurality of regenerative heating devices that supply high-temperature inert gas into the furnace and a plurality of gas burners that supply combustion gas into the furnace, and that is controlled so that the supply of high-temperature inert gas and the supply of combustion gas are carried out independently. As a result, it is said that steel can be heated without oxidation by alternately supplying high-temperature inert gas from the plurality of regenerative heating devices.

[0008] On the other hand, as a technique for generating a predetermined amount of scale, Patent Document 3 discloses a method for heating steel material in which, when steel material to be subjected to hot rolling is heated in a heating furnace, moisture is supplied into the heating furnace to adjust the dew point inside the heating furnace. This promotes oxidation of the steel material surface, and casting defects concentrated within a position of about 0.5 mm from the surface layer of the steel material can be removed together with the scale, thereby improving the surface quality of steel plate products.

[0009] Furthermore, as a technique for controlling the amount of scale generation within an appropriate range, Patent Document 4 discloses a method for heating a slab for hot rolling, in which the scale thickness of the slab when removed from a heating furnace is predicted and the heating temperature and heating time of the slab are set so that the scale thickness becomes a predetermined value.

[0010] JP-A-9-20919, JP-A-2000-248314, JP-A-5-331532, JP-A-7-54036

[0011] However, when conventional techniques are applied to a heating furnace that uses hydrogen or ammonia as a fuel gas to control the amount of scale formation on steel within an appropriate range, the following problems arise.

[0012] The technology described in Patent Document 1 supplies high-temperature non-oxidizing gas into a heating furnace to create a localized non-oxidizing atmosphere around steel materials loaded into the heating furnace. However, when hydrogen or ammonia is burned as fuel gas in the heating furnace, the hydrogen in the fuel gas combines with the oxygen in the combustion air to generate water vapor. Therefore, even if a non-oxidizing atmosphere is created in the heating furnace, there is a problem in that the generated water vapor promotes the growth of scale on the surface of the steel materials.

[0013] The technology described in Patent Document 2 uses a regenerative heating device to recover sensible heat from exhaust gases produced by burning fuel gases using a regenerative heating device, and then passes an inert gas through the regenerative heating device to supply high-temperature inert gas into the heating furnace, thereby suppressing scale growth on steel materials in the heating furnace. However, when hydrogen or ammonia is used as the fuel gas, the regenerative heating device also recovers water vapor from the exhaust gases, so the inert gas passing through the regenerative heating device is humidified before being supplied to the heating furnace. Therefore, as with the above, even if high-temperature inert gas is supplied into the heating furnace, the water vapor promotes scale formation on the steel material surface, making it difficult to control the amount of scale formation within an appropriate range.

[0014] In Patent Document 3, supplying moisture into a heating furnace is expected to promote oxidation of the steel surface and thereby improve the surface quality of steel plate products. However, when hydrogen or ammonia is used as the fuel gas, oxidation of the steel is further promoted, causing excessive growth of scale, which poses a problem that the amount of scale generation cannot be controlled within an appropriate range.

[0015] Patent Document 4 discloses a method for controlling the amount of scale formation by setting the heating temperature and heating time. However, since the internal volume of a steel heating furnace is large, it takes a long time to change the heating temperature. Also, changing the heating time may result in a longer heating time for the steel. In either case, there is room for improvement in that the production efficiency of the heating furnace decreases.

[0016] The present invention has been made to solve the above-mentioned problems, and its object is to provide a method for controlling the amount of scale formation on metallic materials, an apparatus for controlling the amount of scale formation, and a method for operating a heating furnace, for controlling the amount of scale formation within an appropriate range when attempting to reduce carbon dioxide emissions by using hydrogen or ammonia as fuel gas in a heating furnace that heats metallic materials.

[0017] The method for controlling the amount of scale formation according to the present invention, which advantageously solves the above-mentioned problems, is configured as follows.

[0018] [1] A method for controlling the amount of scale formation on a metallic material in a heating furnace, comprising: burner-heating the metallic material using a hydrogen-based gas containing either hydrogen or ammonia or both as fuel; setting a flow rate of the hydrogen-based gas used as fuel for the burner heating as an operational parameter of the heating furnace; and controlling the amount of scale formation on the surface of the metallic material based on the set flow rate of the hydrogen-based gas. [2] A method for controlling the amount of scale formation on a metallic material in the above [1], wherein the metallic material is burner-heated using a mixed gas obtained by mixing the hydrogen-based gas with one or more gases selected from coal gas and hydrocarbon gases as fuel. [3] A method for controlling the amount of scale formation on a metallic material in a heating furnace, comprising: further setting at least one selected from the heating time and heating temperature of the metallic material in the heating furnace as an operational parameter of the heating furnace; and controlling the amount of scale formation on the surface of the metallic material based on the set operational parameter. [4] A method for controlling the amount of scale formation on a metallic material in a heating furnace according to the above-mentioned [1] or [2], wherein the heating furnace includes a preheating zone, a heating zone, and a soaking zone, and wherein burner heating is performed in the soaking zone using a hydrogen-based gas as fuel, a flow rate of the hydrogen-based gas used as fuel for burner heating in the soaking zone is set as an operational parameter of the heating furnace, and the amount of scale formation on the surface of the metallic material is controlled based on the set flow rate of the hydrogen-based gas. [5] A method for controlling the amount of scale formation on a metallic material in a heating furnace according to the above-mentioned [1] or [2], wherein the amount of scale formation on the metallic material is controlled based on the operational parameters of the heating furnace so that the amount of scale formation on the metallic material falls within a predetermined range. [6] A method for controlling the amount of scale formation on a metallic material in a heating furnace according to the above-mentioned [3], wherein the amount of scale formation on the metallic material is controlled based on the operational parameters of the heating furnace so that the amount of scale formation on the metallic material falls within a predetermined range. [7] A method for controlling the amount of scale formation on a metallic material in a heating furnace according to the above-mentioned [4], wherein the amount of scale formation on the metallic material is controlled based on the operational parameters of the heating furnace so that the amount of scale formation on the metallic material falls within a predetermined range.

[0019] The scale formation rate control device and heating furnace operation method according to the present invention, which advantageously solve the above-mentioned problems, are configured as follows. [8] A scale formation rate control device for a metallic material in a heating furnace, comprising a control unit including: an acquisition unit that acquires operating parameters of the heating furnace including a flow rate of a hydrogen-based gas used as fuel for burner heating, the flow rate of which is composed entirely of either hydrogen or ammonia, or both; a prediction unit that predicts the amount of scale formation on the metallic material using the acquired operating parameters; a determination unit that determines whether the predicted amount of scale formation is within a predetermined range; and a setting unit that sets operating parameters of the heating furnace if the predicted amount of scale formation is not within the predetermined range. [9] The scale formation rate control device for a metallic material in a heating furnace according to the above item [8], wherein the acquisition unit acquires operating parameters of the heating furnace including a flow rate of a mixed gas obtained by mixing the hydrogen-based gas with one or more gases selected from coal gas and hydrocarbon gas.

[10] A method for operating a heating furnace for heating a steel material using the method for controlling the amount of scale formation on a metallic material in a heating furnace according to the above item [5].

[11] A method for operating a heating furnace that heats a steel material using the method for controlling the amount of scale formation on a metallic material in a heating furnace described in [6] above.

[12] A method for operating a heating furnace that heats a steel material using the method for controlling the amount of scale formation on a metallic material in a heating furnace described in [7] above.

[0020] According to the present invention, by using hydrogen or ammonia as the fuel gas for the heating furnace, it is possible to reduce carbon dioxide emissions, and by controlling the amount of scale generation within an appropriate range, it is possible to reduce the occurrence of surface defects on the metal material and suppress a deterioration in product yield.

[0021] FIG. 1 is a configuration diagram showing an outline of a heating furnace according to one embodiment. FIG. 2 is a configuration diagram showing the arrangement of burner equipment in a heating furnace. FIG. 3 is a configuration diagram of an example of burner equipment. FIG. 4 is a block diagram showing the outline configuration of hydrogen-based burner equipment for a heating furnace according to one embodiment. FIG. 5 is a configuration diagram of an example of hydrogen-based burner equipment. FIG. 6 is a graph showing the relationship between the scale thickness on the surface of a steel material and the heating time when the amount of steam in the furnace is changed. FIG. 7 is a configuration diagram of a scale formation amount control device according to one embodiment. FIG. 8 is a graph showing the relationship between the scale thickness on the surface of a steel material and the steam concentration in the furnace when the surface temperature of the material to be heated in the furnace is changed.

[0022] The scale formation amount control device for metal materials in a heating furnace according to this embodiment will be described below.

[0023] The scale formation amount control device according to this embodiment includes an acquisition unit that acquires operating parameters of the heating furnace, including the flow rate of a hydrogen-based gas, the total amount of which is hydrogen and / or ammonia, used as fuel for burner heating; a prediction unit that predicts the amount of scale formation of the metal material using the acquired operating parameters; a determination unit that determines whether the predicted amount of scale formation is within a preset range; and a setting unit that sets the operating parameters of the heating furnace if the predicted amount of scale formation is not within the preset range.

[0024] First, a heating furnace equipped with a burner system will be described. <Heating System> Fig. 1 is a schematic cross-sectional view of a heating system for metallic materials according to one embodiment of the present invention. The heating system is a system in which a material to be heated is placed inside and heated to a predetermined temperature. The material to be heated is a metallic material, but it may be either an ferrous metal or a non-ferrous metal as long as it is a metallic material that generates an oxide (hereinafter referred to as scale) on its surface through oxidation. The heating temperature of the material to be heated is 500 to 1400°C. Below, a heating system for heating steel material will be described, with steel material being the metallic material.

[0025] The heating equipment 100 shown in FIG. 1 is installed in a hot rolling line producing, for example, steel plates or steel strips, and heats cast steel to a predetermined heating temperature (approximately 1100 to 1300°C). However, the steel to be heated is not limited to slabs that become steel plate materials, but also includes billets, blooms, and other steel materials that become raw materials for shaped steel, wire rods, steel pipes, and the like. The heating equipment 100 includes a heating furnace 1 that heats the steel by burner heating using a fuel gas containing a hydrogen-based gas whose total amount is either hydrogen or ammonia, or both. The process of heating the metal material to be heated in the heating furnace 1 is called the heating process. Furthermore, the heating equipment 100 preferably includes a control computer 101 that performs data analysis of various operational parameters to control the operation of the heating process.

[0026] <Heating Furnace> The heating furnace 1 includes a charging section 8 for charging (hereinafter also referred to as "carrying in") the steel material S, and an unloading section 9 for unloading (hereinafter also referred to as "extracting") the steel material S. For example, steel material (slabs) produced on a continuous casting line is transported to a yard on the charging side of the heating furnace 1, and is charged into the heating furnace 1 from the charging section 8 according to a production schedule of a hot rolling line or the like.

[0027] The interior of the heating furnace 1 is divided into a plurality of zones, and from the upstream side in the conveying direction of the steel material, these zones are a preheating zone 3 divided into 1 to 3 zones, a heating zone 4 divided into 2 to 8 zones, and a soaking zone 5 divided into 1 to 3 zones. A conveying device 10 is disposed in the heating furnace 1, which conveys the steel material S sequentially from a charging section 8 to an unloading section 9. Each zone of the heating furnace 1 is controlled to a different atmospheric temperature, and as the conveying device 10 conveys the steel material S through the preheating zone 3, heating zone 4, and soaking zone 5 in that order, the average temperature of the steel material S charged into the heating furnace 1 gradually increases until it is heated to a predetermined heating temperature (target heating temperature) in the heating furnace 1.

[0028] The conveying device 10 is equipped with a support mechanism for the steel material S called a skid, and includes a fixed skid 10a that supports the steel material S and a movable skid 10b that lifts and moves the steel material S. The movable skid 10b conveys the steel material S toward the discharge section 9 by repeatedly ascending and descending, moving forward, descending, and retreating within the heating furnace 1.

[0029] A plurality of burners 6 are provided inside the heating furnace 1 along the conveying direction of the steel material S. The burners 6 are arranged to heat the inside of the heating furnace 1 by combustion. When the inside of the heating furnace 1 is heated by the burners 6, the temperature of the steel material S increases due to radiation from the furnace wall of the heating furnace 1. In addition, a flow of atmospheric gas occurs inside the heating furnace 1, and the temperature of the steel material S may increase due to convection. Furthermore, the temperature of the steel material S may increase when the flame of the burner 6 comes into direct contact with the steel material S. In any case, the burners 6 heat the steel material S inside the heating furnace 1 by raising the temperature inside the heating furnace 1.

[0030] The burners 6 are arranged in each of a plurality of zones inside the heating furnace 1. However, the number of zones does not necessarily have to match the number of burners. In the heating furnace 1 shown in FIG. 1, upper burners 6a are arranged on the upper surface side of the steel material S from the charging section 8 toward the discharge section 9, and lower burners 6b are arranged on the lower surface side of the steel material S. Furthermore, the heating furnace 1 shown in FIG. 1 is schematically shown with side burners that spray flames from one side wall surface in the conveying direction of the steel material S toward the opposing side wall surface, but axial burners that spray flames in the same direction as the conveying direction of the steel material S or roof burners that spray flames from the ceiling of the heating furnace into the interior may also be used.

[0031] FIG. 2 shows the piping system of the burners 6 arranged in the heating furnace 1, using some of the zones constituting the heating furnace 6 as an example. The burners 6 (upper burner 6a, lower burner 6b) arranged in the heating furnace 1 are connected to a fuel gas supply system 31 that supplies fuel gas G and a combustion air supply system 32 that supplies combustion air A. The fuel gas supply system 31 and the combustion air supply system 32 are connected to a blower (not shown) and other devices, and supply the fuel gas G and combustion air A to the burners 6. As a result, the fuel gas G and the combustion air A are sprayed from the burners 6, and the fuel gas G is burned by diffusing, generating a flame that is blown into the heating furnace. Air collected from the atmosphere may be used as the combustion air A. However, reformed air, for example, by removing nitrogen from the air or adding pure oxygen, may also be used as the combustion air. Increasing the oxygen content of the combustion air promotes the oxidation reaction of the fuel gas G and reduces the flow rate of the combustion air supplied from the combustion air supply system 32, thereby reducing the power consumption of pumps and other devices. A mixed gas obtained by mixing oxygen with combustion exhaust gas may also be used as the combustion air A. By reducing the oxygen content of the combustion air, the atmosphere inside the heating furnace can be made a reducing atmosphere, and the reduction of nitrogen oxides produced by the combustion of ammonia, etc. can be promoted.

[0032] 3 shows a schematic diagram of a burner system 60 for burner heating. The burner refers to a device that injects a flame into a furnace, and in particular refers to the part that injects the flame into the furnace. The burner system refers to the entire device, including the ancillary devices for injecting the flame.

[0033] The burner equipment 60 includes a burner nozzle 7 that forms a flow path for fuel gas G and combustion air A for spraying a flame by the burner 6, a fuel gas supply system 31 that supplies fuel gas G to the burner nozzle 7, and a combustion air supply system 32 that supplies combustion air A to the burner nozzle 7. The burner nozzle 7 is, for example, a double-pipe nozzle, and fuel gas G is sprayed from the inside toward the furnace interior, while combustion air A is supplied to the outside. As a result, a combustible mixture is formed by mixing the fuel gas G and the combustion air A, and a flame is sprayed from the burner 6 toward the interior of the heating furnace 1.

[0034] The burner equipment 60 may be provided with a fuel gas flow rate control valve 33 for adjusting the flow rate of fuel gas G supplied from the fuel gas supply system 31 to the burner nozzle 7, and a fuel gas flow meter 34 for measuring the flow rate of fuel gas G. This makes it possible to adjust the combustion energy supplied into the heating furnace 1. The burner equipment 60 may also be provided with a combustion air flow rate control valve 35 for adjusting the flow rate of combustion air A supplied from the combustion air supply system 32 to the burner nozzle 7, and a combustion air flow meter 36 for measuring the flow rate of combustion air A. This makes it possible to adjust the air ratio of the fuel gas to the theoretical air amount in the burner 6.

[0035] Furthermore, in addition to the nozzle using the double-pipe nozzle described above, a nozzle mix type burner that mixes fuel gas and combustion air midway through the burner nozzle may be used for the burner equipment 60. In this case, the combustion air may be preheated using exhaust gas or the like before it is mixed with the fuel gas.

[0036] 2, a combustion air flow rate adjustment valve 35 that adjusts the flow rate of combustion air supplied to each burner 6 and a combustion air flow meter 36 that measures the flow rate of combustion air are arranged in a combustion air supply system 32 that supplies combustion air to the burners 6. However, the combustion air flow rate adjustment valve 35 and the combustion air flow meter 36 do not need to be provided for each burner 6, and a plurality of burners may be grouped together, and the flow rate of combustion air may be adjusted for each group.

[0037] <Burner heating using coal gas> Conventional steel heating furnaces have used by-product gases generated in steelworks and other facilities as fuel gas supplied to the burner equipment. By-product gases are primarily derived from coal and are also called coal gases because they are generated due to the incomplete combustion of coal. Coal gases include coke oven gas, blast furnace gas, converter gas, and electric furnace gas. Blast furnace gas is a by-product gas generated when iron ore is reduced in a blast furnace to produce pig iron. Coke oven gas is a by-product gas generated by high-temperature carbonization of coal to produce coke. Converter gas is a by-product gas generated during the steelmaking process in a converter furnace. Electric furnace gas is a by-product gas generated due to the incomplete combustion of auxiliary fuel (recarburizer) used in electric furnaces. By-product gases have various component compositions depending on the process used to generate them.

[0038] For example, the typical composition of blast furnace gas is 21-30% by volume of combustible carbon monoxide, 50-60% by volume of non-combustible nitrogen, and 10-22% by volume of carbon dioxide. The lower heating value of blast furnace gas is 3.45 MJ / Nm ３ The typical composition of coke oven gas is 46-60% by volume of hydrogen, 20-35% by volume of methane, 5-10% by volume of carbon monoxide, and 2-4% by volume of hydrocarbons such as ethylene. The lower heating value of coke oven gas is 18.0 MJ / Nm ３ Converter furnace gas contains approximately 75% by volume of carbon monoxide, approximately 13% by volume of carbon dioxide, and trace amounts of oxygen, nitrogen, and hydrogen. The lower heating value of converter furnace gas is 8.2 MJ / Nm ３ The typical composition of electric furnace gas is about 10% by volume of carbon monoxide, about 22% by volume of carbon dioxide, about 5% by volume of oxygen, and about 56% by volume of nitrogen. The lower heating value of electric furnace gas is 2.8 MJ / Nm ３ Coal gas also includes a gas (sometimes called M gas) that is an appropriate mixture of blast furnace gas, coke oven gas, and converter gas. By mixing coal gases with different calorific values, the amount of heat required to heat the material to be heated can be supplied, ensuring stable operation of the heating furnace.

[0039] <Hydrogen-based burner equipment> In the heating equipment 100 of this embodiment, at least one of the burner equipments arranged in the heating furnace uses a hydrogen-based gas whose entire amount is either hydrogen or ammonia, or both, as a fuel gas. Hereinafter, among the burner equipment arranged in the heating furnace, a burner equipment whose entire amount is either hydrogen or ammonia, or both, is referred to as a hydrogen-based burner equipment. Furthermore, hydrogen and ammonia used as fuel gas are referred to as a hydrogen-based gas.

[0040] First, an embodiment will be described in which a hydrogen-based gas containing either or both of hydrogen and ammonia as the entire fuel is used.

[0041] Hydrogen is a colorless gas at room temperature, with an ignition point of 560°C and a lower calorific value of 10.5 MJ / Nm ３ When hydrogen is burned, the flame temperature is high and the combustion speed is fast, so the tip of the burner nozzle is likely to become hot. For this reason, it is advisable to use a burner nozzle that mixes the hydrogen with combustion air after it is ejected. This allows for slow combustion and reduces the thermal load on the burner nozzle. In a hydrogen-based burner facility that uses hydrogen as fuel gas G, for example, the flow rate of hydrogen injected from the burner is 185 Nm ３ / hr, combustion air flow rate 370-601 Nm ３ Combustion is carried out under the operating conditions of 1000kJ / hr.

[0042] Ammonia is a colorless gas at room temperature, with an ignition point of 651°C and a lower calorific value of 14.1 MJ / Nm ３ When ammonia is burned, the flame temperature is relatively low and the combustion speed is slow, so the ammonia combustion reaction can be stabilized by using a burner nozzle that actively mixes ammonia with combustion air. In a hydrogen-based burner facility that uses ammonia as fuel gas G, for example, the flow rate of ammonia injected from the burner is 185 Nm ３ / hr, combustion air flow rate 370-601 Nm ３ Combustion is carried out under the operating conditions of 1000kJ / hr.

[0043] The hydrogen-based burner equipment 70 applied to this embodiment can be the same as the burner equipment 60 shown in Fig. 3. That is, the hydrogen-based burner equipment 70 is the same burner equipment as the burner equipment that uses coal gas as the fuel gas, but uses hydrogen-based gas HG as the fuel gas G. By using hydrogen-based gas as the fuel gas, the hydrogen-based burner equipment suppresses the generation of carbon dioxide, and therefore the amount of carbon dioxide emitted from the heating furnace can be reduced.

[0044] The configuration of a hydrogen-based burner system 70 applied to this embodiment will be described with reference to Figure 3. The hydrogen-based burner system 70 performs burner heating by injecting a flame into the furnace using hydrogen-based gas HG as fuel gas G and combustion air A. The hydrogen-based burner system 70 includes a burner nozzle 7 for injecting the flame into the furnace, a fuel gas supply system 31 that supplies fuel gas G to the burner nozzle 7, and a combustion air supply system 32 that supplies combustion air A to the burner nozzle 7. The burner nozzle 7 is, for example, a double-pipe nozzle, and fuel gas G is injected into the furnace from the inside, while combustion air A is supplied to the outside. As a result, a combustible mixture is formed by mixing the hydrogen-based gas HG as fuel gas G with the combustion air A, and a flame is injected from the burner 6 into the heating furnace 1.

[0045] The hydrogen-based burner equipment 70 preferably includes a fuel gas flow rate adjustment valve 33 for adjusting the flow rate of fuel gas G supplied from the fuel gas supply system 31 to the burner nozzle 7, and a fuel gas flow meter 34 for measuring the flow rate of fuel gas G. The hydrogen-based burner equipment 70 also preferably includes a flow rate setting unit 47 for setting the flow rate of the hydrogen-based gas. The flow rate setting unit 47 is, for example, a controller, and issues a control command to adjust the valve opening of the fuel gas flow rate adjustment valve 33 so that the actual flow rate measured by the fuel gas flow meter 34 matches a predetermined flow rate setting value of the hydrogen-based gas HG. This makes it possible to control the combustion energy of the flame injected from the hydrogen-based burner equipment 70 into the heating furnace 1 and the amount of carbon dioxide emitted from the heating furnace 1.

[0046] In addition to the flow rate setting unit 47, the hydrogen-based burner equipment 70 preferably includes a steam amount control unit 48 that controls the amount of steam in the heating furnace 1 within a predetermined range. The steam amount control unit 48 is configured, for example, by a computer. The steam amount control unit 48 calculates the amount of steam in the heating furnace 1 and sends a command to the flow rate setting unit 47 to set a flow rate of the hydrogen-based gas HG supplied to the hydrogen-based burner equipment 70 so that the calculated amount of steam in the furnace falls within a predetermined target range of steam amount (target steam range). Since the amount of steam in the heating furnace 1 affects the behavior of scale formation on the surface of the steel material S, the steam amount control unit 48 can control the behavior of scale formation on the surface of the steel material S by sending a command to the flow rate setting unit 47 to set a flow rate of the hydrogen-based gas HG. In this case, it is preferable to install a dew point meter 49 in the heating furnace 1 and estimate the amount of steam in the heating furnace 1 based on dew point information acquired by the dew point meter 49. A method for estimating the amount of steam in the heating furnace 1 will be described later.

[0047] 4 shows an example in which a burner equipment 60 that uses coal gas CG as fuel gas G and a hydrogen-based burner equipment 70 that uses hydrogen-based gas HG as fuel gas G are arranged within the furnace as burners 6 of the heating furnace 1. In this case, a fuel gas supply system that supplies fuel gas G to the burner nozzle 7 of the burner equipment 60 is connected to a supply source of coal gas CG, and the burner equipment 60 injects a flame produced by combustion of coal gas into the heating furnace 1. Meanwhile, a fuel gas supply system that supplies fuel gas G to the burner nozzle 7 of the hydrogen-based burner equipment 70 is connected to a supply source of hydrogen-based gas HG, and the hydrogen-based burner equipment 70 injects a flame produced by combustion of hydrogen-based gas into the heating furnace 1. In this case, the combustion air supply system that supplies combustion air A to the burner equipment 60 and the hydrogen-based burner equipment 70 may be shared by the burner equipment 60 and the hydrogen-based burner equipment 70.

[0048] The heating furnace shown in FIG. 4 includes hydrogen-based burner equipment that uses hydrogen-based gas HG as fuel gas G, compared to conventional heating furnaces in which all burner equipment uses coal gas CG as fuel gas G, and therefore reduces the amount of carbon dioxide emitted from the heating furnace.

[0049] Another embodiment of the hydrogen-based burner equipment will be described, in which a mixed gas obtained by mixing a hydrogen-based gas with one or more gases selected from coal gas and hydrocarbon-based gases is used as the fuel gas. Here, the mixed gas refers to a case in which a hydrogen-based gas containing either or both of hydrogen and ammonia is mixed with coal gas (including hydrogen) or a hydrocarbon-based gas (methane, ethane, propane, etc.).

[0050] The hydrogen-based burner equipment may use a mixed gas containing the hydrogen-based gas HG and other fuels as the fuel gas G. For example, a mixed gas of the hydrogen-based gas and coal gas may be used as the fuel gas G.

[0051] Figure 5 shows another example of a hydrogen-based burner system 71, which uses a mixed gas of hydrogen-based gas HG and coal gas CG as fuel gas G. The hydrogen-based burner system 71 shown in Figure 5 is similar to the hydrogen-based burner system 70 shown in Figure 3 in that it includes a burner nozzle 7 that emits a flame into the heating furnace, a fuel gas supply system 31 that supplies fuel gas G to the burner nozzle 7, and a combustion air supply system 32 that supplies combustion air A to the burner nozzle 7. Also similar is the fact that combustion air A is supplied from the combustion air supply system 32 to the burner nozzle 7, a combustible mixture is formed by mixing the fuel gas G and the combustion air A, and a flame is emitted from the burner 6 toward the inside of the heating furnace.

[0052] 5 includes a mixing unit 40 that mixes a hydrogen-based gas HG supplied through a hydrogen-based gas supply system 45 with a coal gas CG supplied through a coal gas supply system 46. The mixing unit 40 generates a fuel gas G by mixing the hydrogen-based gas HG with the coal gas CG. The fuel gas G generated in the mixing unit 40 is further mixed with combustion air A to form a combustible mixture, which is sprayed as a flame from the burner 6 toward the inside of the heating furnace 1.

[0053] The mixing section 40 refers to a portion where a hydrogen-based gas supply system 45 that supplies a hydrogen-based gas HG and a coal gas supply system 46 that supplies a coal gas CG join together. The hydrogen-based gas HG and the coal gas CG are supplied from their respective supply pipes, and by joining together, mixing is performed without providing a special stirring mechanism. Therefore, the mixing section 40 may be configured as a certain space at the portion where these supply pipes intersect.

[0054] However, the mixing unit 40 may be provided with a static mixing device such as a static mixer or a dynamic mixer having a stirring function, which is preferable in that the hydrogen-based gas HG and the coal gas CG are mixed more uniformly to form a mixed gas.

[0055] The hydrogen-based burner equipment 71 may be provided with a hydrogen-based gas flow rate control valve 41 for adjusting the flow rate of the hydrogen-based gas HG supplied to the mixing section 40 through a hydrogen-based gas supply system 45, and a hydrogen-based gas flow meter 42 for measuring the flow rate of the hydrogen-based gas HG. The hydrogen-based burner equipment 71 may also be provided with a coal gas flow rate control valve 43 for adjusting the flow rate of the coal gas CG supplied from the coal gas supply system 46 to the mixing section 40, and a coal gas flow meter 44 for measuring the flow rate of the coal gas CG.

[0056] These make it possible to adjust the mixture ratio of the hydrogen-based gas HG and the coal gas CG contained in the fuel gas G. When the mixture ratio of the hydrogen-based gas HG contained in the fuel gas G is increased, the effect of reducing carbon dioxide emissions from the heating furnace 1 becomes greater compared to conventional burner heating that uses only coal gas CG as fuel gas.

[0057] On the other hand, when ammonia is used as the hydrogen-based gas, ammonia is a flame-retardant fuel that is more difficult to ignite than general fuel gases and has a slower combustion rate, so if the mixture ratio of ammonia contained in the fuel gas G is high, combustion in the burner 6 may become unstable. By adjusting the mixture ratio of ammonia and coal gas contained in the fuel gas G, it is possible to ensure stable burner heating while reducing carbon dioxide emissions.

[0058] The hydrogen-based burner equipment 71 preferably further includes a flow rate setting unit 47 that sets the flow rate of the hydrogen-based gas HG to be supplied to the mixing unit 40. The flow rate setting unit 47 is, for example, a control controller, and issues a control command to adjust the valve opening of the hydrogen-based gas flow rate adjustment valve 41 so that the actual value of the flow rate measured by the hydrogen-based gas flow meter 42 matches the flow rate set value of the hydrogen-based gas HG that is set in advance. This makes it possible to control the combustion energy of the flame injected from the hydrogen-based burner equipment 71 into the heating furnace 1 and the amount of carbon dioxide emitted from the heating furnace 1.

[0059] Furthermore, the flow rate setting unit 47 may be configured to, in addition to having the function of setting the flow rate of the hydrogen-based gas HG to be supplied to the mixing unit 40, issue a control command to adjust the valve aperture of the coal gas flow rate adjustment valve 43 so that the actual value of the flow rate measured by the coal gas flow meter 44 matches the flow rate set value of the coal gas CG, which is set in advance. This makes it possible to individually set the flow rates of the hydrogen-based gas HG and the coal gas CG to be supplied to the mixing unit 40, and to adjust the combustion energy supplied into the heating furnace 1 and the amount of carbon dioxide emitted from the heating furnace 1.

[0060] The hydrogen-based burner equipment 71 may be provided with a steam amount control unit 48 that controls the amount of steam in the heating furnace 1 within a preset range, in addition to the flow rate setting unit 47. The function of the steam amount control unit 48 is similar to that of the steam amount control unit 48 described above with reference to FIG.

[0061] When M gas, which is coal gas, and hydrogen, which is a hydrogen-based gas, are mixed and burned, the hydrogen mixing ratio (the ratio of the flow rate of hydrogen supplied through the hydrogen-based gas supply system 45 to the flow rate of hydrogen supplied through the M gas and hydrogen-based gas supply system 45) can be selected arbitrarily. For example, if the hydrogen mixing ratio is 60%, the hydrogen flow rate injected from the burner is 111 Nm ３ / hr, M gas flow rate 74 Nm ３ / hr, combustion air flow rate 370-601 Nm ３ / hr. The composition of M gas is 20% by volume of carbon monoxide, 13% by volume of carbon dioxide, 24% by volume of hydrogen, 13% by volume of methane, 1.2% by volume of hydrocarbons such as ethylene, and 28.8% by volume of nitrogen. When M gas and ammonia are mixed and burned, the ammonia mixture ratio (the ratio of the ammonia flow rate supplied through the hydrogen-based gas supply system 45 to the ammonia flow rate supplied through the M gas and hydrogen-based gas supply system 45) becomes high, and therefore the ammonia mixture ratio is about 50%. As an example, if the ammonia mixture ratio is 30%, the ammonia flow rate injected from the burner will be 50 Nm ３ / hr, M gas flow rate 117 Nm ３ / hr, combustion air flow rate 480-624Nm ３ Combustion is carried out under the operating conditions of 1000kJ / hr.

[0062] Next, a scale formation amount control device according to this embodiment will be described. <Scale formation amount control device> The scale formation amount control device according to this embodiment includes a control unit including an acquisition unit that acquires operation parameters of a heating furnace, including a flow rate of a hydrogen-based gas, the total amount of which is hydrogen and / or ammonia, used as fuel for burner heating; a prediction unit that predicts the amount of scale formation on the metallic material using the acquired operation parameters; a determination unit that determines whether the predicted amount of scale formation is within a predetermined range; and a setting unit that sets operation parameters of the heating furnace if the predicted amount of scale formation is not within the predetermined range. The acquisition unit is also capable of acquiring operation parameters of the heating furnace, including a flow rate of a mixed gas obtained by mixing the hydrogen-based gas with one or more gases selected from coal gas and hydrocarbon gas.

[0063] Fig. 7 shows the configuration of a scale generation amount control device according to this embodiment. The scale generation amount control device 51 shown in Fig. 7 is, for example, a general-purpose computer such as a workstation or a personal computer. The scale generation amount control device 51 has a control unit 52, an input unit 53, an output unit 54, and a storage unit 55. The control unit 52 is, for example, a CPU, and executes various programs stored in the storage unit 55, causing the control unit 52 to function as an acquisition unit 56, a prediction unit 57, a determination unit 58, and a setting unit 59.

[0064] The input unit 53 is, for example, a keyboard, a touch panel integrated with a display, or the like. The output unit 54 is, for example, an LCD or CRT display, or the like. The storage unit 55 is, for example, an updatable flash memory, a built-in hard disk or a hard disk connected via a data communication terminal, an information recording medium such as a memory card, or a read / write device for the same. The storage unit 55 stores programs and data for realizing control of the scale generation amount by the scale generation amount control device 51. The storage unit 55 also stores a scale thickness prediction model that has been generated in advance.

[0065] Next, a method for controlling the amount of scale formation on a metallic material in a heating furnace according to this embodiment will be described. <Method for controlling the amount of scale formation> In the method for controlling the amount of scale formation according to this embodiment, a metallic material is burner-heated using a hydrogen-based gas containing either or both of hydrogen and ammonia as fuel, the flow rate of the hydrogen-based gas used as fuel for burner heating is set as an operational parameter of the heating furnace, and the amount of scale formation on the surface of the metallic material is controlled based on the set flow rate of the hydrogen-based gas. It is also possible to burner-heat a metallic material using a mixed gas as fuel, in which the hydrogen-based gas is mixed with one or more gases selected from coal gas and hydrocarbon gases.

[0066] Here, the amount of scale formed refers to the thickness or amount of scale formed on the surface of the metal material to be heated. The operating parameters of the heating furnace refer to the operating conditions of the heating furnace that affect the heating state of the material to be heated in the heating furnace.

[0067] In the heating furnace 1, burner heating is performed using hydrogen-based gas HG, and water vapor is generated by the combustion of hydrogen and ammonia contained in the fuel gas G. In this situation, water penetrates through the surface of the metal material in the heating furnace 1, and the oxygen constituting the water molecules oxidizes the metal material in the heating furnace 1 while releasing hydrogen. The hydrogen diffuses into the oxide layer formed on the surface of the metal material and combines with the oxygen in the oxide layer at the interface between the oxide layer and the base material to generate water vapor. The generated water vapor then further oxidizes the metal material, promoting the formation of the oxide layer. Therefore, in a heating furnace that uses hydrogen or ammonia as fuel gas, water vapor contained in the combustion gas penetrates the interface with the oxide layer of the metal material and promotes the oxidation of the metal material, making it difficult to suppress scale formation on the metal material even when the heating furnace is controlled to a non-oxidizing atmosphere.

[0068] On the other hand, if there are foreign matters, such as impurities generated during casting or mold powder mixed in during casting, on the surface of the metal material before it is charged into the heating equipment 100, the combustion of hydrogen-based gas can promote the formation of scale on the metal material. Therefore, after the metal material is transported out of the heating equipment 100, the oxide layer can be removed using a descaling device or the like, thereby suppressing the occurrence of surface defects on the metal material.

[0069] In this embodiment, it is preferable to provide the hydrogen-based burner equipment with a flow rate setting unit 47 to control the flow rate of the hydrogen-based gas HG. By changing the flow rate of the hydrogen-based gas HG, the amount of water vapor generated in the heating furnace 1 changes, and this makes it possible to control the thickness of the oxide layer formed on the surface of the metal material.

[0070] Furthermore, it is preferable to provide a water vapor amount control unit 48 that controls the amount of water vapor in the heating furnace 1 within a preset range, and to set a flow rate set value for the hydrogen-based gas HG to be supplied to the hydrogen-based burner equipment 70, 71 to the flow rate setting unit 47 based on the amount of water vapor in the heating furnace 1 calculated by the water vapor amount control unit 48. In this case, it is preferable that the water vapor amount control unit 48 estimates the amount of water vapor in the heating furnace 1 based on dew point information acquired by a dew point meter 49 installed in the heating furnace 1, and sends a command to the flow rate setting unit 47 for the flow rate set value of the hydrogen-based gas HG to be supplied to the hydrogen-based burner equipment 70, 71 so that the estimated amount of water vapor falls within a preset target range for the amount of water vapor (target water vapor range). This makes it possible to control the amount of scale formation on the surface of the metal material during the heating process.

[0071] A method for estimating the amount of water vapor in the heating furnace 1 performed by the water vapor amount control unit 48 will be described. First, the water vapor amount control unit 48 acquires a measured value of the dew point of the atmospheric gas acquired by the dew point meter 49. From the acquired measured value of the dew point, the water vapor pressure of the atmospheric gas is calculated using a known relationship between the amount of saturated water vapor and temperature. Then, the volume fraction of water vapor contained in the atmospheric gas is calculated from the calculated water vapor pressure and the pressure (total pressure) of the atmospheric gas, and the amount of water vapor in the heating furnace 1 can be calculated using the internal volume of the heating furnace 1. As a known relationship between the amount of saturated water vapor and temperature, for example, the Tenens equation or the Murray equation may be applied. In this way, the water vapor amount control unit 48 can estimate the amount of water vapor in the heating furnace 1.

[0072] As an example of a method for controlling the amount of scale formation on a metallic material, an example of heating a steel material will be described. In the method for controlling the amount of scale formation on a metallic material of this embodiment, the steel material S is preferably heated so that its surface temperature reaches 1000 to 1250°C in the heating step. In the heating step, burner heating using hydrogen-based gas HG is performed in a furnace, and the water vapor contained in the combustion gas of the hydrogen-based gas HG promotes oxidation of the steel material S, allowing a predetermined scale thickness to be formed by the time the heating step is completed. As a result, even if the steel material before the heating step contains impurities generated during casting or foreign matter resulting from mold powder mixed in during casting, the occurrence of surface defects can be suppressed by removing the scale using a descaling device or the like after the heating step is completed.

[0073] However, if the heating temperature is less than 1000°C, scale of an appropriate thickness may not be formed, so the heating temperature is set to 1000°C or higher. The heating temperature is more preferably 1050°C or higher. On the other hand, if the heating temperature exceeds 1250°C, the thickness of the scale formed in the heating step becomes too large, resulting in a decrease in product yield, so the heating temperature is set to 1250°C or lower. The heating temperature is more preferably 1200°C or lower.

[0074] Here, it is known that the scale growth of the steel material in the heating furnace 1 is diffusion-limited, and increases exponentially with respect to the surface temperature, as shown in formula (1). Here, ξ is the scale thickness (μm), A is the frequency factor (1 / s), Q is the activation energy (J / mol), T is the surface temperature of the steel (K), R is the gas constant (J / molK), and t is the elapsed time (s). The frequency factor is a value that represents the number of times reacting molecules collide with each other per unit time. The frequency factor A and activation energy Q vary depending on the chemical composition of the steel, and are therefore determined in advance by experimentation for each type of steel to be subjected to the heating process.

[0075] It may be difficult to directly measure the temperature of the steel material S transported inside the heating furnace 1. Therefore, it is preferable to estimate the surface temperature of the steel material S in the heating furnace 1 using a temperature model for calculating the temperature of the steel material S, and control the operating conditions of the heating process so that the estimated temperature becomes the target heating temperature. In this case, the temperature model of the steel material in the heating furnace takes into account the effect of radiant heat from the furnace walls onto the steel material. The surface temperature of the steel material is calculated based on the measured ambient temperature in the heating furnace and position information (tracking information) of the steel material within the heating furnace. The temperature model of the steel material is preferably installed in a control computer (process computer) 101 to perform temperature calculations. A method for temperature calculation can be used in which the steel material is represented by a mesh divided into finite sections in the thickness and width directions, and the temperatures at the thickness and width directions are calculated by solving the heat conduction equation using the finite difference method or the finite element method. In this case, the surface temperature of the steel material is the temperature calculated for the mesh located at the outermost layer in the thickness direction.

[0076] In the heating step, it is preferable to further control the amount of steam in the heating furnace 1 to 10 to 30% by volume by setting the flow rate of the hydrogen-based gas HG used for burner heating. If the amount of steam in the heating furnace 1 in which the heating step is performed is less than 10% by volume, the thickness of the scale formed on the surface of the steel material may be insufficient. On the other hand, if the amount of steam in the heating furnace 1 exceeds 30% by volume, scale on the surface of the steel material is likely to grow, and excessive scale may be formed.

[0077] FIG. 6 shows an example of an investigation into the thickness of scale formed on the surface of steel material S after heating the steel material S for a predetermined time in a heating process, with the heating temperature set to 1050°C and the steam content in the furnace controlled to 5, 15, and 25 volume percent. Here, when the target thickness of the scale formed on the surface of the steel material is set to 350 μm or more and the reference heating time in the heating process is set to 60 minutes (3600 seconds), FIG. 6 reveals that when the steam content in the heating furnace is as low as 5 volume percent, the thickness of the scale formed on the surface of the steel material does not reach the target thickness. In this case, the operating conditions for the heating furnace require the heating time to be extended beyond the reference value, which results in a problem of reduced production efficiency of the heating equipment 100. On the other hand, when the steam content in the heating furnace is set to 15 or 25 volume percent, the thickness of the scale formed on the surface of the steel material is equal to or greater than the target thickness, and it is considered possible to form sufficient scale to remove casting defects and the like present on the surface of the steel material.

[0078] In the burner heating of the above embodiment, in addition to setting the flow rate of the hydrogen-based gas used as the fuel for burner heating, it is preferable to set at least one of the heating time and heating temperature of the metal material in the heating furnace as an operating parameter of the heating furnace. This is because, as shown in Equation (1) above, scale growth of steel in the heating furnace 1 is diffusion-limited and is affected by the heating time and heating temperature. For example, by increasing the flow rate of the hydrogen-based gas used as the fuel for burner heating to promote scale formation in the heating furnace and shortening the heating time of the metal material in the heating furnace to a predetermined time, the production efficiency of the heating equipment can be improved while ensuring an appropriate amount of scale formation. Furthermore, by increasing the flow rate of the hydrogen-based gas used as the fuel for burner heating to promote scale formation in the heating furnace and lowering the heating temperature of the metal material in the heating furnace to a predetermined temperature, the fuel consumption rate of the heating equipment can be improved while ensuring an appropriate amount of scale formation.

[0079] Furthermore, when the heating furnace includes a preheating zone, a heating zone, and a soaking zone, it is preferable to control the amount of scale formation on the metallic material by setting the flow rate of the hydrogen-based gas used as fuel for burner heating in the soaking zone as an operation parameter of the heating furnace. The preheating zone 3, heating zone 4, and soaking zone 5 of the heating furnace 1 are often controlled to different ambient temperatures, with the soaking zone 5 having the highest ambient temperature. Because scale formation on metallic materials is promoted under conditions of high ambient temperature, the amount of scale formation on the metallic material can be significantly changed by changing the flow rate of the hydrogen-based gas.

[0080] In another embodiment of the method for controlling the amount of scale formation, the operating parameters of the heating furnace are set so that the amount of scale formation on the surface of the heated material is within a predetermined range. This prevents the occurrence of surface defects in the metal material and further suppresses a decrease in product yield. Here, the amount of scale formation will be described using the thickness of scale formed on the surface of the heated material as an example.

[0081] In another embodiment, a target thickness (hereinafter referred to as the target scale thickness) of the scale (oxide layer) formed on the surface of the metallic material during the heating process is set in advance. The target scale thickness is preferably set to a thickness equivalent to a predetermined thickness from the surface of the metallic material before the heating process, where impurities generated during casting and foreign matter resulting from mold powder mixed in during casting are distributed. For example, the target scale thickness of the metallic material to be heated may be set to approximately 50 to 1000 μm. When the metallic material is a steel material, the target scale thickness may be set to 300 to 600 μm. This is because impurities generated during casting and foreign matter resulting from mold powder mixed in during casting are often present in large amounts within a range of approximately 300 to 600 μm from the surface of the steel material.

[0082] The thickness of scale formed on the surface of a metallic material during a heating process can be estimated using a mathematical model that models the growth behavior of oxides (hereinafter referred to as a scale thickness prediction model). For example, the scale growth of a steel material can be estimated using the following equation (2): where f is the oxygen partial pressure PO ２and water vapor partial pressure PH ２ The function f is determined in advance through offline heating experiments as a function of O. It is known that the oxygen partial pressure and water vapor partial pressure affect the scale growth behavior, but it is difficult to formulate this theoretically. Therefore, it is advisable to conduct experiments in advance in which the metallic material is heated while changing the oxygen partial pressure and water vapor partial pressure, and determine the function f by regression analysis so that the thickness of the scale formed on the surface of the metallic material satisfies the above formula (2).

[0083] The scale thickness prediction model determined in advance as described above may be loaded into the control computer 101 that sets the operating conditions of the heating equipment 100, and a predicted value for the thickness of scale formed on the surface of the metallic material may be calculated based on information acquired by the control computer 101 from the heating furnace 1.

[0084] Specifically, the operation parameters of the heating furnace 1 are acquired from the control computer 101 (acquisition step). Next, the scale thickness at the stage of completing the heating process is predicted based on the acquired operation parameters of the heating furnace 1 (prediction step). Then, it is determined whether the predicted scale thickness (predicted scale thickness) is within a preset range of target scale thickness (determination step). In the determination step, if the predicted scale thickness is within the range of the target scale thickness, a command is issued to the control computer 101 to maintain the current operation conditions of the heating furnace 1. On the other hand, in the determination step, if the predicted scale thickness is not within the range of the target scale thickness, a setting command is issued to the control computer 101 to change the operation parameters of the heating furnace 1 (setting step).

[0085] The setting step sends a setting command to the control computer 101 for the operating parameters of the heating furnace 1, which use the flow rate of the hydrogen-based gas used as fuel for burner heating. In addition to the flow rate of the hydrogen-based gas, the heating time and heating temperature of the heating process may also be used. Changing the flow rate of the hydrogen-based gas HG used in the heating process changes the amount of water vapor generated by burner heating, thereby controlling the amount of scale generated on the metal material. Furthermore, changing the heating time of the heating process changes the thickness of the oxide layer of the metal material generated in the heating process. Furthermore, changing the heating temperature of the heating process (the ambient temperature in each zone inside the heating furnace) changes the thickness of the oxide layer of the metal material generated in the heating process. In this case, the heating temperature of the heating process can be changed by changing the ambient temperature of the soaking zone.

[0086] Next, the process of controlling the amount of scale formation by the scale formation control device 51 will be described. The acquisition unit 56 acquires operational parameters of the heating furnace 1 from the control computer 101. The acquisition unit 56 acquires, as the operational parameters of the heating furnace 1, the flow rate of the hydrogen-based gas HG used as fuel for the hydrogen-based burner equipment 70, 71 of the heating furnace 1. The acquisition unit 56 acquires, as the operational parameters of the heating furnace 1, the set values ​​of the heating time and heating temperature of the metal material in the heating furnace 1. The acquisition unit 56 may also acquire measured values ​​of the temperature and dew point of the atmospheric gas in the heating furnace 1.

[0087] When the prediction unit 57 acquires the operational parameters of the heating furnace 1 from the acquisition unit 56, it reads out the scale thickness prediction model stored in the storage unit 55. The prediction unit 57 inputs the operational parameters of the heating furnace 1 into the scale thickness prediction model and causes the model to output a predicted value of the scale thickness (predicted scale thickness), thereby predicting the amount of scale generation. The prediction unit 57 may display the predicted predicted scale thickness on the output unit 54. This allows the operator to visually check the output unit 54 and confirm the predicted value of the amount of scale generation in the heating process.

[0088] Next, the process of determining the predicted scale thickness by the scale generation amount control device 51 will be described. The prediction unit 57 outputs the predicted scale thickness to the determination unit 58. The determination unit 58 determines whether the predicted value of the scale thickness obtained from the prediction unit 57 is within the range of the target scale thickness. The target scale thickness may be obtained from the control computer 101 and stored in the memory unit 55. The target scale thickness may be input by the operator from the input unit 53, or may be input in advance by the operator and stored in the memory unit 55. The determination unit 58 outputs the determination result as to whether the predicted value of the scale thickness is within the range of the target scale thickness to the setting unit 59.

[0089] When the setting unit 59 receives a determination result from the determining unit 58 that the predicted scale thickness is within the range of the target scale thickness, the setting unit 59 outputs to the control computer 101 a command to maintain the current operational parameters of the heating furnace 1, since the operational parameters of the heating furnace 1 acquired by the acquiring unit 56 can be used to control the furnace to a predetermined target scale thickness range. On the other hand, when the setting unit 59 receives a determination result from the determining unit 58 that the predicted scale thickness is not within the range of the target scale thickness, the setting unit 59 changes the operational parameters of the heating furnace 1 acquired by the acquiring unit 56. In this case, the setting unit 59 assumes new set values ​​for the operational parameters of the heating furnace 1 obtained by changing the current set values, and outputs the new set values ​​to the predicting unit 57. The predicting unit 57 again inputs the new set values ​​into the scale thickness prediction model, predicts the scale thickness, and outputs the new set values ​​to the determining unit 58. The determining unit 58 determines whether the newly acquired predicted value of the scale thickness is within the range of the target scale thickness. The predicting unit 57 and the determining unit 58 repeat this process until the predicted value of the scale thickness is within the range of the target scale thickness. The setting unit 59 then identifies the operating parameters of the heating furnace 1 that will bring the predicted value of the scale thickness into the range of the target scale thickness, and outputs these to the control computer 101.

[0090] The control computer 101 controls the heating equipment 100 based on the information acquired from the setting unit 59 so as to realize the set operation parameters of the heating furnace 1 .

[0091] The effects of this embodiment will be specifically described below based on examples, but the present invention is not limited to these examples.

[0092] As an example of the present invention, an example of controlling the amount of scale formation on a steel material using a test device that simulates the above-mentioned heating process will be described. The test device used in this example is a combustion gas heating furnace that performs burner heating.

[0093] The combustion gas heating furnace used in the heating process had internal dimensions of 800 mm high x 500 mm wide x 1000 mm long. The combustion gas heating furnace was equipped with burners on the top and bottom surfaces of the test specimens to be placed inside the furnace, and was configured to supply a mixed gas of hydrogen-based gas and coal gas from a fuel gas supply system. The hydrogen-based gas used in the mixed gas was ammonia, and the coal gas used was M gas, a mixture of by-product gases generated in steelworks.

[0094] The combustion conditions used in the example were ammonia flow rate of 50 Nm ３ / hr, M gas flow rate 117 Nm ３ / hr, the ammonia volume ratio in the mixed gas was 30%, and the M gas volume ratio was 70%. The M gas used had a composition that would result in 13% by volume of carbon dioxide being emitted into the exhaust gas under complete combustion conditions. On the other hand, in the example, the burner heating conditions were set so that the carbon dioxide concentration in the exhaust gas in the heating step would be 9% by volume by adjusting the ammonia mixing ratio.

[0095] In the examples, the metal material to be heated was carbon steel with a plate thickness of 220 mm, a plate width of 300 mm, and a plate length of 500 mm. The heated material was machined from a cast slab, and a Φ0.5 mm K-sheathed thermocouple was attached to the center of the plate width and length at a depth of 2 mm from the surface. This allowed the temperature rise behavior of the heated material during the heating process to be measured, and the surface temperature of the heated material was estimated based on the measurement results.

[0096] Here, the heating conditions in the combustion gas heating furnace were changed in advance to investigate the relationship between the heating temperature and the thickness of scale formed on the surface of the heated material. Figure 8 shows the relationship between the water vapor concentration in the combustion gas heating furnace and the thickness of scale on the heated material for each heating temperature. The heating time was 60 minutes. Regarding the thickness of scale, when the surface temperature set in the combustion gas heating furnace was reached, the heated material was removed from the combustion gas heating furnace and immediately water-cooled. This prevented further scale growth. Then, an evaluation sample was machined from the heated material, and the cross section of the heated material was observed under an optical microscope to determine the thickness of scale.

[0097] From FIG. 8, it can be seen that the scale thickness of the material to be heated can be controlled by changing the water vapor concentration in the combustion gas heating furnace according to the heating temperature.

[0098] Next, a scale thickness prediction model was created based on the results of the preliminary experiment shown in Figure 8 as well as the results of investigations in which the heating time was changed. For the scale thickness prediction model, a mathematical model that models the oxide growth behavior shown in Equation (2) was used. The created scale thickness prediction model was stored in the memory unit 55 of the scale formation amount control device 51, and the amount of scale formation on the metallic material was controlled by setting the flow rate of the hydrogen-based gas used as fuel for burner heating as an operation parameter of the heating furnace.

[0099] Here, the target scale thickness of the carbon steel used for the heated material was set to a range of 350 to 600 μm. The range of the carbon steel used for the heated material, including impurities generated during casting and foreign matter resulting from mold powder mixed in during casting, was previously identified, and the target scale thickness was set within this range. In other words, if the scale thickness generated on the evaluation sample taken from the heated material is less than 350 μm, the scale thickness may be insufficient and surface defects may occur when the material is subjected to hot rolling or other processes. On the other hand, if the scale thickness exceeds 600 μm, excessive scale generation may result in a decrease in product yield. Based on the above, a case where the scale thickness generated on the evaluation sample taken from the heated material was within the target scale thickness range of 350 to 600 μm was determined to be pass (◯). On the other hand, a case where the scale thickness generated on the evaluation sample taken from the heated material was outside the target scale thickness range of 350 to 600 μm was determined to be fail (×).

[0100] The heating conditions and test results are shown in Table 1. The "heating temperature," "hydrogen-based gas," and "mixing ratio of hydrogen-based gas" in Table 1 represent the initial conditions for the preset operating parameters of the heating furnace. The "operational parameters of the heating furnace to be changed" indicate the operating parameters that the setting unit 59 resets when the determining unit 58 determines that the predicted value of the scale thickness is not within the range of the target scale thickness. In this case, conditions 5 and 6 mean that the setting unit 59 resets the heating time or heating temperature in addition to the hydrogen-based gas flow rate as the operating parameter to be reset. Meanwhile, the "water vapor amount" indicates the water vapor concentration in the furnace after the operating parameters of the heating furnace are set by the setting unit 59. The "scale thickness" indicates the scale thickness obtained by observing the cross section of the heated material by an optical microscope after an evaluation sample is taken in the same manner as above.

[0101]

[0102] As can be seen from Table 1, under conditions 1 to 8, which are examples of the invention, the scale thickness formed on the evaluation samples taken from the heated material was within the target scale thickness range of 350 to 600 μm, and was therefore judged to be acceptable (◯). In particular, under conditions 3 and 4, despite the heating temperature being set at a relatively high 1100°C, the amount of water vapor in the furnace was controlled to be low, so the scale thickness of the heated material was within the target scale thickness range. On the other hand, under condition 8, the heating temperature was set at a relatively low 1050°C, and the mixture ratio of hydrogen-based gas was low, making it difficult to promote scale formation. However, by controlling the hydrogen-based gas flow rate, the scale thickness of the heated material was within the target scale thickness range.

[0103] In contrast, in the comparative examples, conditions 9 and 10, even when the judgment unit 58 determined that the predicted value of the scale thickness was not within the range of the target scale thickness, heating was performed under the preset initial conditions, and the scale thickness of the heated material did not fall within the range of the target scale thickness.

[0104] From the above, it was found that this example makes it possible to reduce carbon dioxide emissions by using hydrogen or ammonia as fuel gas for the heating furnace, and also to control the amount of scale formation within an appropriate range, thereby reducing the occurrence of surface defects on the metal material.

[0105] 100 Heating equipment 101 Control computer S Steel material D Steel material conveying direction A Combustion air G Fuel gas CG Coal gas HG Hydrogen gas 1 Heating furnace 3 Preheating zone 4 Heating zone 5 Uniformity zone 6 Burner 6a Upper burner 6b Lower burner 7 Burner nozzle 8 Charging section 9 Discharge section 10 Conveying device 10a Fixed skid 10b Moving skid 13 Exhaust duct 31 Fuel gas supply system 32 Combustion air supply system 33 Fuel gas flow control valve 34 Fuel gas flow meter 35 Combustion air flow control valve 36 Combustion air flow meter 37 Furnace wall 38 Furnace interior 40 Mixing section 41 Hydrogen-based gas flow control valve 42 Hydrogen-based gas flow meter 43 Coal gas flow control valve 44 Coal gas flow meter 45 Hydrogen-based gas supply system 46 Coal gas supply system 47 Flow rate setting unit 48 Water vapor amount control unit 49 Dew point meter 51 Scale formation amount control device 52 Control unit 53 Input unit 54 Output unit 55 Memory unit 56 Acquisition unit 57 Prediction unit 58 Determination unit 59 Setting unit 60 Burner equipment 70, 71 Hydrogen-based burner equipment

Claims

1. A method for controlling the amount of scale formation on a metallic material in a heating furnace, comprising: heating the metallic material with a burner using a hydrogen-based gas containing either or both of hydrogen and ammonia as fuel; setting a flow rate of the hydrogen-based gas used as fuel for the burner heating as an operation parameter of the heating furnace; and controlling the amount of scale formation on the surface of the metallic material based on the set flow rate of the hydrogen-based gas.

2. A method for controlling the amount of scale formation on a metallic material in a heating furnace as set forth in claim 1, wherein the metallic material is heated with a burner using as fuel a mixed gas obtained by mixing the hydrogen-based gas with one or more gases selected from coal gas and hydrocarbon-based gas.

3. A method for controlling the amount of scale formation on a metallic material in a heating furnace as described in claim 1 or 2, further comprising setting at least one selected from a heating time and a heating temperature of the metallic material in the heating furnace as an operational parameter of the heating furnace, and controlling the amount of scale formation on the surface of the metallic material based on the set operational parameter.

4. A method for controlling the amount of scale formation on a metallic material in a heating furnace as claimed in claim 1 or 2, wherein the heating furnace includes a pre-heating zone, a heating zone and a soaking zone, burner heating is performed in the soaking zone using a hydrogen-based gas as fuel, a flow rate of the hydrogen-based gas used as fuel for burner heating in the soaking zone is set as an operation parameter of the heating furnace, and the amount of scale formation formed on the surface of the metallic material is controlled based on the set flow rate of the hydrogen-based gas.

5. A method for controlling the amount of scale formation on a metallic material in a heating furnace as described in claim 1 or 2, in which the amount of scale formation on the metallic material is controlled based on the operating parameters of the heating furnace so that the amount of scale formation on the metallic material is within a preset range.

6. A method for controlling the amount of scale formation on a metallic material in a heating furnace as described in claim 3, wherein the amount of scale formation on the metallic material is controlled based on the operating parameters of the heating furnace so that the amount of scale formation on the metallic material falls within a preset range.

7. A method for controlling the amount of scale formation on a metallic material in a heating furnace as set forth in claim 4, wherein the amount of scale formation on the metallic material is controlled based on the operating parameters of the heating furnace so that the amount of scale formation falls within a preset range.

8. A device for controlling the amount of scale formation on metallic materials in a heating furnace, comprising a control unit including: an acquisition unit for acquiring operating parameters of the heating furnace including a flow rate of a hydrogen-based gas, the total amount of which is either hydrogen or ammonia or both, used as fuel for burner heating; a prediction unit for predicting the amount of scale formation on the metallic material using the acquired operating parameters; a determination unit for determining whether the predicted amount of scale formation is within a preset range; and a setting unit for setting the operating parameters of the heating furnace if the predicted amount of scale formation is not within the preset range.

9. A device for controlling the amount of scale formation on metal materials in a heating furnace as described in claim 8, wherein the acquisition unit acquires operation parameters of the heating furnace including a flow rate of a mixed gas obtained by mixing the hydrogen-based gas with one or more gases selected from coal gas and a hydrocarbon-based gas.

10. A method for operating a heating furnace for heating steel material using the method for controlling the amount of scale formation on metallic materials in a heating furnace as claimed in claim 5.

11. A method for operating a heating furnace for heating steel material using the method for controlling the amount of scale formation on metallic materials in a heating furnace as claimed in claim 6.

12. A method for operating a heating furnace for heating steel material using the method for controlling the amount of scale formation on metallic materials in a heating furnace as claimed in claim 7.

Images